Telephone plug



0. L. COOK TELEPHONE PLUG July 26, 1960 2 Sheets Sheet 1 Filed May 5, 1956 INVENTOR. 0m 1. c-4

AZ- J o. cooK July 26, 1960 TELEPHONE PLUG 2 Sheets-Sheet 2 Filed May 3, 1956 m m w m United States Patent This invention relates to telephone plugs and comprises a new and improved combination headset-microphone plug used on microphone head set assemblies to connect them with other components of an intercornmunication system.

The quality of a plug of the type disclosed in the instant application is determined by a number of very important considerations, both physical and electrical in nature. The ability of'a plug to withstand considerable physical abuse and to transmit electrical signals in the order of millivolts with a negligible drop in potential across the plug are but two of the requirements of an acceptable assembly.

Plugs of the type disclosed are frequently used as a part of an intercommunication system in aircraft. As a result, they are subjected to extreme atmospheric conditions. This use also makes it essential that the plug not exceed rather minute physical proportions. 'It will be appreciated that the limitation as to size creates a number of mechanical and electrical problems. For example, the small quantity of insulation-which may be introduced between independent electrical connectors within the plug makes it impossible to use most of the well known insulating materials, for they will not furnish sufiicient electrical resistance between the connectors to allow the plug to tunction properly. It is necessary to select a material which has an extremely high electrical resistance and at the same time has a high dielectric strength, low

an inert, non-brittle substance. a

One important object of my invention is to minimize the electrical resistance between terminal posts and their contacts in a telephone plug. f

Another important object of my invention is to provide a plug sutfici-ently rugged soas to be capable of withstanding without harmful effect all of the physical tests to which itmay be subjected.

Still another important object of my invention is to provide a plug of limited size and which contains an Water absorption properties, dimensional stability, and is insulating material introducing at least 100 megohms of resistance between each of the electrical connectors.

Additional requirements must be met before a plug may be considered to be of superior quality. These requirements will be recognized in the objects of my invention listed in the following paragraphs.

Other important objects of my invention are to provide a telephone plug capable of being connected to cords of diiferent 7 sizes; to prevent twisting or longitudinal movement of the cord relative to the plug adjacent the terminal posts; and to provide a little slack in the cord between the point of breakout of the individual electrica wires of the cord and the terminal posts.

Still another important object of my invention is to provide a telephone plug whose insulating material and internal electrical connections are unafiected by the heat resulting'from the soldering or unsoldering of a wire or wires to a terminal post.

fl C

To accomplish these and other objects, I provide as one important feature of my invention two electrical connectors which include integrally formed terminal posts and ring contacts. The ring cont-acts surround a central stem which carries at its end a ball contact. The ball contact and stem are integrally formed with a strain relief anchor, the ball .and anchor being disposed at opposite extremes of the plug. An opening formed in the stem. is closed about another terminal post and this post together with the ball contact define a third electrical connector in the plug. Y

A body for'the plug surrounds the mid-sections of the stem and electrical connectors. A collar depends from the central .portion of thebody, surrounds the upper portion of the stem, and serves as a third ring contact for the plug. A fourth terminal post electrically connected to the collar is press fitted into a recess formed in the body. The four terminal posts and their respective contacts are insulated from one another by a plastic material, preferably a filled Kel-F, a productof the M. W. Kellogg Company, which fills the cavities between each of the parts of the plug.

Extending upwardly from the plastic fill and surrounding the four terminal posts is a multi-pronged clamp having a cooperating band which presses the prongs against the cord connected to the plug. The assembly. is completed by a shell or cap threaded on the lower end and which screws onto a threaded section of the body. The cap covers the clamp and holds it in position, as well as covering the various electrical connections made between the wires in the cord and the terminal posts.

These and other objects and features of my invention along with incident advantages will be better understood and appreciated from the following detailed description of one embodiment thereof, selected for purposes of illustration and shown in the accompanying drawings, in which:

Figure 1 is a view in perspective of a stem forming part of a plug constructed in accordance with my invention,

Figure 2 is a view in perspective of the stem shown in Figure, 1, illustrating the manner in which the first electrical connector is mounted on it,

. Figure 3 is a view in perspective including all of the components shown in Figure 2 and illustrates the manner in which another electrical connector is incorporated into the assembly,

Figure 4 is a view in perspective of the assembly shown in Figure 3 with the bodyyand its terminal post added,

Figure 5 is a view in perspective of the assembly shown in Figure 4 with the terminal post added to the stem,

Figure 6 is a view in perspective of the assembly shown in Figure 5 with the plastic fill added,

Figure 7 is a perspective view of the assembly shown in Figure 6 with a clamp and its cooperating band added,

' Figure 8 is a view in perspective of the completed assembly as it appears connected to atelephone cable, and

Figure 9 is a view in perspective of another embodi- 60 ment of a clamp which may be incorporated into my invention. i

The preferred embodiment of my invent-ion lllustrated in the drawing will be described in detail by setting forth the manner in which the device is assembled. Referring first to Figure 1, the assembly is organized about a stem 10, which is integrally formed with a ball contact 12 ,and

a strain relief anchor 14. A cylindrical collar 16, having a transverse'opening 118 through its center, is formed on the mid-section of the stem 10 immediately below the strain relief anchor 14. The stem 10, preferably made I of nickel silver, forms the central component about which all the other components of theplug are oriented,

A shaft 20, forming part of the stem and interconnecting the ball contact 12 with the collar 16, is surrounded at its lower terminal portion by a ring contact 22, forming part of an electrical connector 24. In addition to the ring contact 22, the connector 24 includes a midsection 26 and a terminal post 28.

The mid-section or stem 26 of the connector 24 is bent slightly to displace the terminal post 28 some distance from the face of the strain relief anchor 14. The ring contact 22, the stem 26 and the terminal post 28, are formed as a single unit from one piece of nickel silver stock. As is clearly illustrated in the drawings, the

central bore 30 of the ring contact 22 is considerably larger than the shaft 20 of the stem 10, and the anchor 14, so that it may be slid over the stem into the position illustrated.

After the connector 24 has been slipped into the position illustrated in Figure 2, a second electrical connector 32, substantially identical to the connector 24, is placed in the position illustrated in Figure 3. The connector 32 includes a ring contact 34, a central stem 36, and a terminal post 38 formed as an integral unit from nickel silver. The ring contact 34 assumes the position illustrated by inserting the anchor 14 and the terminal post 28 through its central bore 40.

After the connector 32 is assembled, a body. 42, having a central opening 44 and a depending collar 46, is slipped over the terminal posts 28 and 38 and the anchor 1-4 to the position illustrated in Figure 4. This is easily accomplished by virtue of the fact that the opening 44 is quite large, and considerable freedom of movement is afforded the connectors 24 and 3.2 on the shaft 20 of the stem. The outer cylindrical wall 48 of the body 42 is threaded as shown at 50 and defines a rather shallow housing for the terminal posts 28 and 38. A recess 52 which may be slightly tapered is formed in the body 42 and receives a terminal post 54. The post 54 is in direct electrical communication with the depending collar 46 of the body.

Next a terminal post 56, having a depending stem 58 in the form of a right angle is fitted in the opening 18 in the collar 16 of the main stem 10. The diameter of the opening 18 is somewhat larger than the diameter of the stem 58. Thus in order to insure proper electrical contact between the ball 12 and the terminal post 56, the collar 16 is compressed to close the opening 18 against the stem 58.

The components of my telephone plug described in detail in the preceding paragraphs are shown in their assembled form in Figure 5. Preferably, each of these components is made of nickel silver. After they have been assembled in the position shown, the entire unit is nickel plated. The plating performs the obvious finishing functions, and more important, enhances the electrical contact between the terminal post 54 and the body 42, as well as the contact between the terminal post 56 and the stem 10.

Before I proceed further with the description of my plug, the four independent electrical connectors will be traced. First of all, the ball contact 12 through the shaft 20 and the collar 16 is in direct electrical communication with the terminal post 56. The ball contact 12 and the terminal post 56 may be referred to as the first contact and terminal, respectively. The second electrical connector is defined by the ring contact 22 and the terminal post 28 which are integrally connected by the stem 26. These elements may be referred to as thesecond contact and terminal respectively. The ring contact 34 and the terminal post 38 comprise the third contact and terminal respectively. These elements are also formed from a single blank of nickel silver. The fourth and last electrical connector in my plug is defined by the collar 46 and the terminal post 54 which are in direct electrical communication by virtue of their being part of the body 42.

The collar 46 and the post 54 may be referred to as the fourth contact and terminal respectively.

The next step in the manufacture of my plug is to place the assembly shown in Figure 5 in a mold and introduce the plastic fill 58, preferably a filled Kel-F. The material fills the shallow well formed in the body 42 by the annular wall 48 and flows down between the rings 46, 34 and 22, separating each from the other and from the shaft 20 of the stem 10. In this manner, the four sets of contacts and terminals are electrically insulated from each other and all of the components are firmly held in position. It will be noted in Figure 6 that the filled Kel-F" forms a collar about the lower portion of the anchor 14 and extends upwardly a distance at least as high as the upper terminal portions of the four posts. It will also be noted in that figure that a pair of oppositely disposed slots 60 are formed in the sides of the fill 58.

A clamp 62, as shown in Figure 7, comprising a ring 64 and a pair of depending legs 66 is mounted on the assembly shown in Figure 6 with the legs 66 registering with the slots 60 in the filled Kel-F. The ring 64 lies an appreciable distance above the ends of the terminal posts and the anchor 14, and carries a number of fingers 68 which surround a cable suggested at 70. The fingers 68 each include a built up head 69 having a smooth inner surface 71 which grips the cord or cable 70. The smooth surfaces of the heads prevent the breaking of the cord cover and the wires running through it when the cord is bent about the end of the fingers.

A band 72 made of rather strong tempered metal is tightened around the fingers 68 within the grooves 73 formed in them to hold the cable 70 in place. The grooves 73 prevent the band from riding up on the heads 69 and sliding off the fingers. While the anchor 14 is connected to the center strand in the cable to take the load off the terminal posts when the cable is pulled, the fingers 68 grip the cable to prevent it from twisting relative to the plug and, in addition, prevent strain from being exerted on the terminal .posts when the cable is pressed in the direction of the plug.

In use, a cable is connected to the plug by inserting the ends of the wires into recesses 74 formed in each of the terminal posts. Any conventional means, such as soldering may be used to secure the individual wires to their posts. However, before the individual connections are made, the center strand of the cable is secured to the strain anchor 14 by tying it in the hole provided in the anchor for that purpose.

Next, the band 72 is firmly tightened against the fingers 68 to press them securely against the cable 70. After this has been done, it is only necessary to screw the cap or shell 76 on to the threaded portion 50 of the body 42. The cap 76 hides and protects the individual connections made between the wires in the cable and the terminal posts, holds the clamp 62 in position on the fill 58 and makes the assembly more attractive.

In Figure 9 I have illustrated an alternative embodiment of a clamp 80 which may be used in place of the clamp 62 shown in Figure 7. The clamp 80 includes a lower ring 82 having a pair of downwardly extending legs 84 which are positioned to slide into the slots 60 formed in the sides of the insulation. Extending upwardly from the ring 82 is a curved wall 86 having a circumferentially directed recess 88 formed in its outer surface. The clamp is completed by a second ring 90 which is integrally formed with the other structure. A cord connected to the plug will pass downwardly through the ring 90, and a band identical to the band 72 shown in Figure 7 and having its central portion disposed within the recess 88 will hold it in position and accomplish the same function as the heads 69 of the fingers 68.

From the foregoing description it will be appreciated that a rather simple, strong and electrically desirable plug has been provided. The number of individual elements whlch make up the plug has been reduced to a minimum to increase the strength and ruggedness of theplug while substantially reducing electrical resistance between the contacts and terminals of each of the'connectors. The unit is simple to use, easy to connect to a cable, and free of all the many undesirable features present in other plugs now on themarket and which are intended to perform the same function. r

The illustrated embodiment of my plug may be made extremely small. The overall length of the plug from the upper end of the cap to the opposite end of the ball contact 12 and its maximum diameter may be 2 1 and or less respectively without sacrificing performance. It will also be noted that no solder is employed in the connectors between the terminals and the contacts. wire is soldered to one of the posts, the heat incident to the soldering can not adversely afiect the individual connectors in the plug.

Each of the clamps shown and described permits a little slack in the wires between their point of breakout from the cord and their connections to the terminals. Moreover, the clamps and anchor .14 prevent twisting, pushing or pulling of the cord relative to the plug from adversely affecting the connections between the wires and the terminals. The filled Kel-F provides adequate resistance between each of the connectors and is not adversely affected by either unusual atmospheric conditions, excessive heat, or other extreme conditions Which may be present.

.Those skilled in the art will appreciate that certain modifications may be made of the illustrated embodiment of my invention without departing from the spirit thereof. For example, althoughspecific materials have been named as preferable for use in the manufacture of my plug, certain applications of the assembly shown may make it desirable to change them.

Such a variance as the type suggested in the preceding paragraph should not be considered a departure from my invention. Therefore, I do not intend to limit the breadth of my invention to the specific embodiment illustrated and described, but rather the scope of my invention should be determined by the appended claims and their equivalents.

What I claim as new and desire to secure by Letters Patent of the United States is:

!l. A four wire plug comprising a stem having a ball contact at one end, three spaced-apart ring contacts surrounding the stem, means electrically insulating the four contacts from each other, a first terminal post electrically connected to the stem, means including second and third terminal posts respectively formed as unitary structures with two of the ring contacts from a single piece of stock, said means extending through the central opening of the third ring contact adjacent the stem, and a fourth terminal post electrically connected to the other of the ring contacts.

2. A plug comprising a plurality of concentric unperforated annular contacts, a stem made of conductive material extending through the centers of the annular contacts, a ball contact secured to one end of the stem, said ball and stem being formed from asingle piece of conducting material, at least one additional stem made of conducting material connected to one of the ring contacts and extending through the centers of other of the ring contacts, said additional stem and its ring contact being formed from a single piece of conducting material, terminal posts secured to the stems, and means electric-ally insulating the contacts and their respective stems and terminal posts from one another.

3. In a plug, a stem, a ball contact formed from a single piece of conducting material with the stem and disposed at one end of the stem, a first unperforated annular contact surrounding the stem adjacent the ball contact, a second unperforated annular contact surrounding the stem and disposed adjacent the first annular contact,

Thus, when a an additional stem formed from a single piece of conducting material with the first annular contact and extending through the center of the second annular contact toward the other end of the first-named stem, a terminal post formed as one piece with the additional stem and the first annular contact and disposed adjacent the other end of the first-named stem, and means electrically insulating the contacts and their respective stems and terminal post from one another.

4. A plug as defined in claim 3 further characterized by a strain relief anchor integrally formed as one piece with the first-named stem at its other end, a third stem formed from a single piece of conducting material with the second annular contact and extending toward the other end of the first-named stern, and a terminal post formed as one piece with the third stem adjacent said other end.

5. A telephone plug comprising a stem having a ball contact at one end and a strain relief anchor at its other end, said stem, ball contact and anchor being formed as a unitary structure from a single piece of electrically conductive stock, a second stem having an annular contact at one end which surrounds the first-named stem adjacent the ball contact and a terminal post at its other end, said second stem with its ring contact and terminal post being formed as a unitary structure from a single piece of electrically conductive stock, a third stern having an annular contact at one end which surrounds the firstnamed and second stems and having a terminal post at its other end, said third stern and its annular contact and terminal post being formed as a unitary structure from a single piece of electrically conductive stock, a body member having a depending collar which surrounds all of the stems, said stems being disposed parallel to one another and said terminal posts being disposed parallel to one another and displaced radially outward from the firstnamed stem a distance greater than the inner radius of the annular contacts and collar, and means electrically insulating the stems and their respective contacts from one another.

6. A four wire telephone plug comprising a stem having a ball contact at one end and a strain relief at its other end, the stem and ball contact formed as a unitary structure from a single piece of stock, a terminal post connected to the stem, a second stern having a ring contact at one end which surrounds the first-named stem adjacent the ball contact and a terminal post at its other end, said second stem with its ring contact and terminal post formed as a unitary structure from a single piece of stock, a third stem having a ring contact at one end which surrounds the first-named stem and the second stern and having a terminal post at its other end, said third stem and its ring contact and terminal post formed as a unitary structure from a single piece of stock, a body member having a depending collar which surrounds all of the stems, said collar serving as a fourth contact, a recess formed in the body, a fourth terminal post press fitted into the recess in the body, and means electrically insulating the four contacts and their respective terminal posts from one another.

7. .A telephone plug as defined in claim 6 further characterized by each of the terminal posts being displaced from the first named stern a distance greater than the inner radius of the ring contacts.

8. A plug comprising a plurality of spaced apart and concentrically disposed ring contacts, a conducting stem extending through the center of the ring contacts and having at its end a ball contact disposed beyond the last of the ring contacts, at least one additional conducting stem electrically connected to one of the ring contacts and extending through the center of other of the ring contacts, said additional stem and its ring contact being formed from a single piece of conducting material, and means electrically insulating the contacts and their respective 2,039,957 Hall Mcy 5, v1936 conducing stems from one another. 2,323,575 Snowberger July 6, 1943 2,530,415 Wilson Nov. 21,1950

References Cited in the file of this patent 2,857,581 Henning Oct. 21, 1958 UNITED STATES PATENTS 5 FOREIGN PATENTS 1,680,430 Pacent Aug. 14, 1928 578,576 Great Britain July 3, 1946 

